Intracellular movements of fluorescently labeled synaptic vesicles in frog motor nerve terminals during nerve stimulation

W J Betz, Guy Smith Bewick, R M Ridge

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We stained synaptic vesicles in frog motor nerve terminals with FM1-43 and studied changes in the shape and position of vesicle clusters during nerve stimulation. Each stained vesicle cluster appeared as a fluorescent spot. During repetitive nerve stimulation the spots gradually dimmed, most without changing shape or position. Occasionally, however, a spot moved, appearing in some cases to stream toward and coalesce with a neighboring spot. This suggests the existence of translocation mechanisms that can actively move vesicles in a coordinated fashion between vesicle clusters. Within single clusters, we saw no signs of such directed vesicle movements. Fluorescent spots in terminals viewed from the side with a confocal microscope did not shrink toward the presynaptic membrane during nerve stimulation, but dimmed uniformly. This suggests that vesicles continuously mix within a cluster during destaining and provides no evidence of active vesicle translocators within single vesicle clusters for moving vesicles to the presynaptic membrane.
Original languageEnglish
Pages (from-to)805-813
Number of pages9
Issue number5
Publication statusPublished - 1 Nov 1992



  • Animals
  • Electric Stimulation
  • Fluorescent Dyes
  • Microscopy, Fluorescence
  • Motor Neurons
  • Movement
  • Nerve Endings
  • Rana pipiens
  • Synaptic Vesicles

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